Significant investment is flowing into the development of low-cost and simple-to-operate aircraft for personal transportation. Much effort has focused primarily upon developing new cockpit displays that simplify navigation and improve pilot situational awareness. Many of such in-cockpit displays present colorful, graphical representations of the information gathered by onboard instrumentation. The attractiveness of such displays, however, can distract the pilot and divert his attention away from outside the cockpit. Safety concerns attendant with a distracted pilot are evident.
Concerns with pilots looking down at the displays have led to the development of Heads-Up Display (HUD) technology. In general, HUD technology provides a graphical depiction of flight-critical information optically superimposed on a real-world background. With such information appearing on the real-world background, the focus of the pilot's attention remains outside of the cockpit. While looking outside, the pilot can see the information gathered by the aircraft's instrumentation, such as the position of other aircraft, current flight path direction, and navigation waypoints.
U.S. Pat. No. 4,453,163, issued to Garner et al, describes a heads-up-display with a row of lamps embedded on the rear surface of the propeller. This lamp placement requires the removal of material from the propeller to accommodate the lamps and their means of electrical interconnection. In addition, these lamps are vulnerable to damage by foreign objects (gravel and similar debris). Moreover, the structural characteristics of the propeller (e.g., bending stiffness, strength, mass distribution) are affected by adding or removing structural material from the propeller to accommodate the lamps. These disadvantages preclude the use of this heads-up display with existing propellers, because the modification of the propellers would likely compromise their performance and safety.
Many other challenges have impeded wide-scale adoption of HUD technology in light aircraft, including the need for high-brightness displays, practical limitations in HUD system weight, limited field of view, and viewing angle limitations (i.e., narrow optical aperture) that make displays produced by the HUD system viewable only to the pilot. Moreover, current HUD systems are typically expensive and heavy, some systems weighing as much as 60 pounds. Further, the distance of the displayed information from the pilot's eyes is typically significantly shorter than the focal depth of the background, and thus optics are needed to enable the pilot to focus on the information and the background simultaneously. Accordingly, HUD systems have made little progress in being adopted in light aircraft. There remains, therefore, a need for a heads-up display technology that enables graphical information to be overlaid on the real-world background and avoids the aforementioned focal depth, field of view, size, weight, and cost disadvantages of present-day systems.